Can end and method for fixing the same to a can body

ABSTRACT

A can end ( 22 ) comprising a peripheral cover hook ( 23 ), a chuck wall ( 24 ) dependent from the interior of the cover hook, an outwardly concave annular reinforcing bead ( 25 ) extending radially inwards from the chuck wall, and a central panel ( 26 ) supported by an inner portion ( 27 ) of the reinforcing bead, characterised in that, the chuck wall ( 24 ) is inclined to an axis perpendicular to the exterior of the central panel at an angle between 20° and 60°, and the concave cross-sectional radius of the reinforcing bead ( 25 ) is less than 0.75 mm.

[0001] This invention relates to an end wall for a container and moreparticularly but not exclusively to an end wall of a can body and amethod for fixing the end wall to the can body by means of a doubleseam.

[0002] U.S. Pat. No. 4,093,102 (KRASKA) describes can ends comprising aperipheral cover hook, a chuck wall dependent from the interior of thecover hook, an outwardly concave annular re-inforcing bead extendingradially inwards from the chuck wall and a central panel joined to aninner wall of the reinforcing bead by an annular outwardly convex bead.This can end is said to contain an internal pressure of 90 psi by virtueof the inclination or slope of the chuck wall, bead outer wall and beadinner wall to a line perpendicular to the centre panel. The chuck wallslope D° is between 14° and 16°, the outer wall slope E is less than 4°and the inner wall slope C° is between 10 and 16° leading into theoutwardly convex bead. We have discovered that improvements in metalusage can be made by increasing the slope of the chuck wall and limitingthe width of the anti peaking bead.

[0003] U.S. Pat. No. 4,217,843 (KRASKA) describes an alternative designof can end in which the countersink has inner and outer flat walls, anda bottom radius which is less than three times the metal thickness. Thecan end has a chuck wall extending at an angle of approximately 24° tothe vertical. Conversely, our European Patent application EP0340955Adescribes a can end in which the chuck wall extends at an angle ofbetween 12° and 20° to the vertical.

[0004] Our European Patent No. 0153115 describes a method of making acan end suitable for closing a can body containing a beverage such asbeer or soft drinks. This can end comprises a peripheral flange or coverhook, a chuck wall dependant from the interior of the cover hook, anoutwardly concave reinforcing bead extending radially inwards from thechuck wall from a thickened junction of the chuck wall with the bead,and a central panel supported by an inner portion of the reinforcingbead. Such can ends are usually formed from a prelacquered aluminiumalloy such as an aluminium magnesium manganese alloy such as alloy 5182.

[0005] Our International Patent Application published no. WO93/17864describes a can end suitable for a beverage can and formed from alaminate of aluminium/manganese alloy coated with a film of semicrystalline thermoplastic polyester. This polyester/aluminium alloylaminate permitted manufacture of a can end with a narrow, and thereforestrong reinforcing bead in the cheaper aluminium manganese alloy.

[0006] These known can ends are held during double seaming by an annularflange of chuck, the flange being of a width and height to enter theanti-peaking bead. There is a risk of scuffing if this narrow annulusslips. Furthermore a narrow annular flange of the chuck is susceptibleto damage.

[0007] Continuing development of a can end using less metal, whilststill permitting stacking of a filled can upon the end of another, thisinvention provides a can end comprising a peripheral cover hook, a chuckwall dependent from the interior of the chuck wall, an outwardly concaveannular reinforcing bead extending radially inwards from the chuck wall,and a central panel supported by an inner portion of the reinforcingbead, characterised in that, the chuck wall is inclined to an axisperpendicular to the exterior of the central panel at an angle between30° and 60°, and the concave bead narrower than 1.5 mm (0.060″).Preferably, the angle of the chuck wall to the perpendicular is between40° and 45°.

[0008] In a preferred embodiment of the can end an outer wall of thereinforcing bead is inclined to a line perpendicular to the centralpanel at an angle between −15° to +15° and the height of the outer wallis up to 2.5 mm.

[0009] In one embodiment the reinforcing bead has an inner portionparallel to an outer portion joined by said concave radius.

[0010] The ratio of the diameter of the central panel to the diameter ofthe peripheral curl is preferably 80% or less.

[0011] The can end may be made of a laminate of thermoplastic polymerfilm and a sheet aluminium alloy such as a laminate of a polyethyleneteraphthalate film on an aluminium-manganese alloy sheet or ferrousmetal typically less than 0.010 (0.25 mm) thick for beverage packaging.A lining compound may be placed in the peripheral cover hook.

[0012] In a second aspect this invention provides a method of forming adouble seam between a can body and a can end according to any precedingclaim, said method comprising the steps of:

[0013] placing the curl of the can end on a flange of a can bodysupported on a base plate, locating a chuck within the chuck wall of thecan end to centre the can end on the can body flange, said chuck havinga frustoconical drive surface of substantially equal slope to that ofthe chuck wall of the can end and a cylindrical surface portionextending away from the drive surface within the chuck wall, causingrelative motion as between the assembly of can end and can body and afirst operation seaming roll to form a first operation seam, andthereafter causing relative motion as between the first operation seamand a second operation roll to complete a double seam, during theseseaming operations the chuck wall becoming bent to contact thecylindrical portion of the chuck.

[0014] Various embodiments will now be described by way of example andwith reference to the accompanying drawings in which:

[0015]FIG. 1 is a diagrammatic sketch of known apparatus for forming adouble seam;

[0016]FIG. 2 is an enlarged sectioned side view of a known chuck and canend before seaming;

[0017]FIG. 3 is a sectioned view of a fragment of a known double seam;

[0018]FIG. 4 is a sectioned side view of a can end according to thisinvention before edge curling;

[0019]FIG. 5 is a sectioned side view of the can end of FIG. 4 on a canbody before forming of a double seam;

[0020]FIG. 6 is a like view of the can end and body during firstoperation seaming;

[0021]FIG. 7 is a like view of the can end and body during final secondoperation seaming to create a double seam;

[0022]FIG. 8 is a fragmentary section of a chuck detail; and

[0023]FIG. 9 is a side view of the cans stacked one on the other.

[0024] In FIG. 1 apparatus for forming a double seam comprises a baseplate 1, an upright 2 and a top plate 3.

[0025] A lifter 4 mounted in the base plate is movable towards and awayfrom a chuck 5 mounted in the top plate. The top plate supports a firstoperation seaming roll 6 on an arm 7 for pivotable movement towards andaway from the chuck. The top plate also supports a second operationseaming roll 8 on an arm 9 for movement towards and away from the chuckafter relative motion as between the first operation roll and can end onthe chuck creates a first operation seam.

[0026] As shown in FIG. 1 the chuck 5 holds a can end 10 firmly on theflange 11 of a can body 12 against the support provided by the lifterplate 4. Each of the first operation roll 6 and second operation roll 7are shown clear of chuck before the active seam forming profile of eachroll is moved in turn to form the curl of the can end and body flange toa double seam as shown in FIG. 3.

[0027]FIG. 2 shows on an enlarged scale the chuck 5 and can end 10. Thecan end comprises a peripheral curl 13, a chuck wall 14 dependent fromthe interior of the curl, an outwardly concave anti-peaking bead 15extending inwards from the chuck wall to support a central panel 16.Typically the chuck wall flares outwardly from the vertical at an angleC about 12° to 15°.

[0028] The chuck 5 comprises a body 17 having a threaded bore 18permitting attachment to the rest of the apparatus (not shown). Anannular bead 19 projects from the body 17 of the chuck to define withthe end face of the body a cavity to receive the central panel 16 of thecan end. The fit of panel 16 in annulus 19 may be slack between panelwall and chuck.

[0029] The exterior surface of the projecting bead 19 extends upwardstowards the body at a divergent angle B of about 12° to the vertical tojoin the exterior of the chuck body 17 which tapers off an angle A° ofabout 4° to a vertical axis perpendicular to the central panel. Theouter wall of the chuck 5 engages with the chuck wall at a low positionmarked “D” within the 12° shaped portion of the chuck bead 15.

[0030] As can ends are developed with narrower anti-peaking beads thechuck bead 19 becomes narrower and more likely to fracture. There isalso a risk of scuffing of the can end at the drive position D which canleave unacceptable unsightly black marks after pasteurisation.

[0031]FIG. 3 shows a sectioned fragment of a typical double seam showinga desirable overlap of body hook 21 and end hook 20 between the can end10 and can body 12.

[0032]FIG. 4 shows a can end, according to the invention, comprising aperipheral cover hook 23, a chuck wall 24 extending axially and inwardlyfrom the interior of the peripheral cover hook, an outwardly concavereinforcing or anti-peaking bead 25 extending radially inwards from thechuck wall, and a central panel 26 supported or an inner portion panelwith 27. The panel wall is substantially upright allowing for any metalspring back after pressing. The chuck wall is inclined to an axisperpendicular to the exterior of the central panel at an angle C₁between 20° and 60°; preferably between 40° and 45°. Typically the crosssectional radius of the antipeaking bead is about 0.5 mm.

[0033] Preferably the anti-peaking bead 25 is parallel sided, howeverthe outer wall may be inclined to a line perpendicular to the centralpanel at an angle between −15° to +15° and the height h₄ of the outerwall may be up to 2.5 mm.

[0034] This can end is preferably made from a laminate of sheet metaland polymeric coating. Preferably the laminate comprises an aluminiummagnesium alloy sheet such as 5182, or aluminium manganese alloy such as3004 with a layer of polyester film on one side. A polypropylene filmmay be used on the “other side” if desired.

[0035] Typical dimensions of the example of the invention are: d5overall diameter (as stamped) 65.83 mm d4 PC diameter of seaming panelradius 61.54 mm d3 PC diameter of seaming panel/chuck wall radius 59.91mm r₁ seaming panel/chuck wall radius 1.27 mm r₂ seaming panel radius5.56 mm r₃ concave radius in antipeaking bead <1.5 mm d₂ maximumdiameter of antipeaking bead 50.00 mm d₁ minimum diameter of antipeakingbead 47.24 mm h₂ overall height of can end 6.86 mm h₁ height to top ofantipeaking bead 5.02 mm h₃ panel depth 2.29 mm h₄ outer wall height1.78 mm c chuck wall angle to vertical 43°

[0036] From these dimensions it can be calculated that the ratio ofcentral panel diameter of 47.24 mm to overall diameter of can end 65.84is about 0.72 to 1.

[0037] For economy the aluminium alloy is in the form of sheet metalless than 0.010″ (0.25 mm). A polyester film on the metal sheet istypically 0.0005″ (0.0125 mm).

[0038] Although this example shows an overall height h₂ at 6.86 mm wehave also found that useful can ends may be made with an overall heightas little as 6.35 mm (0.25″).

[0039]FIG. 5 shows the peripheral flange 23 of can end 22 of FIG. 4resting on the flange 11 of a can body 12 before formation of a doubleseam as discussed with reference to FIG. 1.

[0040] In FIG. 5 a modified chuck 30 comprises a chuck body 31 having afrustoconical drive surface 32 engaging with the chuck wall 24 of thecan end 22.

[0041] The frustoconical drive surface is inclined outwardly and axiallyat an angle substantially equal to the angle of inclination C° ofbetween 20° and 60°; in this particular example on chuck angle C of 43°is preferred. The drive surface 32 is a little shorter than the chuckwall 24 of the chuck body. The substantially cylindrical surface portion33, rising above the drive surface 32, may be inclined at an anglebetween +4° and −4° to a longitudinal axis of the chuck. As in FIG. 2,this modified chuck 30 has a threaded aperature to permit attachment tothe rest of the double seam forming apparatus (not shown).

[0042] In contrast to the chuck of FIG. 2 the modified chuck 30 isdesigned to dive initially on the relatively large chuck wall 32 withoutentering deeply into the anti-peaking bead 25. Further drive is obtainedat the juncture of chuck wall 32 and cylindrical wall 33 as chuck wallof end 24 is deformed during 1^(st) and 2^(nd) operation seaming FIGS. 6and 7. The chuck 30 shown in FIG. 5 has an annular bead of arcuate crosssection but this bead is designed to enter the chuck wall withoutscratching or scuffing a coating on the can end; not to drive on theconcave bead surface as shown in FIG. 2.

[0043] It will be understood that first operation seaming is formedusing apparatus as described with reference to FIG. 1.

[0044]FIG. 6 shows the modified can end and chuck during formation of afirst operation seam shown at the left of FIG. 2 as formed by a firstoperation roll 34 adjacent the interfolded peripheral flange of the canend and flange 11 body 12.

[0045] During relative rotation as between the can end 22 and firstoperation roll 34 the edge between the chuck drive wall 32 andcylindrical wall 33 exerts a pinching force between chuck 30 and roll 34to deform the chuck wall of the can end as shown.

[0046] After completion of the first operation seam the first operationroll is swung away from the first operation seam and a second operationroll 38 is swung inwards to bear upon the first operation seam supportedby the chuck 30. Relative rotation as between the second operation roll38 and first operation seam supported by a chuck wall 30 completes adouble seam as shown in FIG. 7 and bring the upper portion 24 of thechuck wall 24 to lie tightly against the can body neck in asubstantially upright attitude as the double seam is tightened by pinchpressure between the second operation roll 38 and chuck 30.

[0047] Can ends according to the invention were made from aluminiumalloy 5182 and an aluminium alloy 3004/polymer laminate sold byCarnaudMetalbox under the trade mark ALULITE. Each can end was fixed bya double seam to a drawn and wall ironed (DWI) can body using variouschuck angles and chuck wall angle as tabulated in Table 1 which recordsthe pressure inside a can at which the can ends failed: TABLE 1 PRESSUREIN BAR (PSIG) TO FAILURE FOR CAN END DATA VARIOUS SEAMING CHUCK ANGLESB° Minimum CHUCK 23° 10°/23° Material Diameter Wall with D. with D.Sample Thickness D1 Angle Seam Seam Code mm mm “C” 23° 10°/23° 4°/23°Ring Ring A ALULITE 52.12 21.13° 5.534 5.734 5.311 6.015 5.875 0.23(2.052″) (80.20) (83.10) (76.97) (87.17) (85.14) B 5182 52.12 21.13°5.599 5.575 5.381 5.935 5.895  0.244 (2.052″) (81.15) (80.79) (77.99)(86.01) (85.43) C 5182 52.12 21.13° 6.004 5.910 5.800 6.224 6.385  0.245(2.052″) (87.02) (85.65) (84.06) (90.21) (92.54) D ALULITE 51.92 21.13°5.334 5.229 5.238 5.730 5.404  0.23 (2.044″) (77.31) (75.78) (75.91)(83.04) (78.32) E 5182 51.92 21.13° 5.555 5.514 5.354 5.895 5.930  0.224(2.044″) (80.50) (79.92) (77.60) (85.43) (85.94) F 5182 51.92 23°  5.839 5.804 5.699 6.250 6.435  0.245 (2.044″) (84.63) (84.12) (82.59)(90.58) (93.26) G ALULITE 51.92 23°   5.123  0.23 (2.044″) (74.25) H5182 (51.92) 23°   5.474  0.224 (2.044″) (79.34) I 5182 51.92 23°  5.698  0.245 (2.044″) (82.58)

[0048] The early results given in Table 1 showed that the can end shapewas already useful for closing cans containing relatively low pressures.It was also observed that clamping of the double seam with the “D” seamring resulted in improved pressure retention. Further tests were doneusing a chuck wall angle and chuck drive surface inclined at nearly 45°:Table 2 shows the improvement observed: TABLE 2 Chuck Angles B° Sample43° with Code h₂ mm (inches) h₃ mm (inches) h₄ mm (inches) 43° seam ringJ 6.86 (0.270) 2.39 (0.094) 2.29 (0.09) 4.89 (70.9) 6.15 (89.1) K 7.11(0.280) 2.64 (0.104) 2.54 (0.10) 4.83 (70.0) 5.98 (86.6) L 7.37 (0.290)2.90 (0.114) 2.79 (0.11) 4.74 (68.7) 6.44 (93.3)

[0049] Table 2 is based on observations made on can ends made ofaluminium coated with polymer film (ALULITE) to have a chuck wall lengthof 5.029 mm (0.198″) up the 43° slope.

[0050] It will be observed that the container pressures achieved forsamples J, K, L, 4.89 bar (70.9 psig), 4.83 bar (70.0 psig) and 4.74 bar(68.7 psig) respectively were much enhanced by clamping the double seam.

[0051] In order to provide seam strength without use of a clamping ring,modified chucks were used in which the drive slope angle C° was about43° and the cylindrical surface 33 was generally +4° and −4°. Resultsare shown in Table 3. TABLE 3 Results LINING CHUCK SAMPLE COM- ANGLESCODE MATERIAL POUND DRIVE/WALL PRESSURE c 0.224 5182 with 43° 4.60(66.7) g 0.23 Alulite with 43°/4°  5.45 (79.0) h 0.224 5182 with 43°/4° 6.46 (93.6) j 0.23 Alulite without 43°/4°  5.91 (85.6) k 0.244 5182without 43°/4°  6.18 (89.6) l 0.23 Alulite without 43°/−4° 5.38 (77.9) m0.25 Alulite without 43°/−4° 6.20 (89.8) n 0.23 Alulite without 43°/0° 6.11 (88.5) o 0.25 Alulite without 43°/0°  6.62 (95.9)

[0052] Table 3 shows Code “O” made from 0.25 mm Alulite to give 6.62 bar(95 psi) Pressure Test Result indicating a can end suitable forpressurised beverages. Further chucks with various land lengths (slope)were tried as shown in Table 4. TABLE 4 CHUCK WALL ANGLE 43°/0° 1.27 MMLAND R. 43°/0° 1.9 mm 0.5 MM LAND SHARP TRANSITION BLEND VARIABLE NO. D.SEAM WITH D. SEAM NO. D. SEAM WITH D. SEAM CODE RING RING RING RING 76.699 (97.08) 7.017 (101.7) 6.779 (98.24) 7.006 (101.54) 8 6.315 (91.52)6.521 (94.5) 6.293 (91.2)  6.236 (90.37)  9 6.095 (88.33) 6.30 (91.3)6.238 (90.4)  6.719 (97.38) 

[0053] Table 4 shows results of further development to seaming chuckconfiguration to bring closer the pressure resistance of ring supportedand unsupported double seams.

[0054] Table 4 identifies parameters for length of generally verticalcylindrical surface 33 on the seaming chuck 30 and also identifies apositional relationship between the chuck wall 24 of the end and thefinished double seam. It will be understood from FIG. 7 shows that theforces generated by thermal processing or carbonated products aredirected towards and resisted by the strongest portions of the completeddouble seam.

[0055] Table 5 shows results obtained from a typical seam chuck designedto give double seam in accordance with parameters and relationshipsidentified in Table 4. Typically: As shown in FIG. 8 the chuck comprisesa cylindrical land of length ‘1’ typically 1.9 mm (0.075″) andfrustoconical drive surface 32 inclined at an angle Y°, typically 43°,to the cylindrical to which it is joined by a radius R typically 0.5 mm(0.020″). Angle “X” is typically 90°. TABLE 5 DIMENSIONS mm PRESSURECODE GAUGE h₂ h₃ bar (psi) 20 .23 mm 7.37 (.290″)  2.36 (.093″)  6.383(92.6) 21 .23 mm 7.37 (.290″)  2.36 (.093″)  6.402 (92.8) with compound26 .23 mm 6.87 (.2705″) 2.37 (.0935″) 6.144 (89.88) 27 .23 mm 6.87(.2705″) 2.37 (.0934″) 6.071 (88.0) with compound 28 .23 mm 7.37(.290″)  2.36 (.093″)  6.414 (93.0) 29 .23 mm 7.37 (.290″)  2.84(.112″)  6.725 (97.5) 30 .23 mm 6.86 (.270″)  2.37 (.0935″) 6.062 (87.9)31 .23 mm 6.86 (.270″)  2.37 (.0935″) 6.013 (87.2) 34 .25 mm 7.37(.290″)  2.87 (.113″)  7.787 (112.9) 36 .25 mm 7.32 (.288″)  2.34(.092″)  7.293 (105.8) 37 .25 mm 7.32 (.288″)  2.34 (.092″)  7.402(107.3) with compound 38 .25 mm 6.87 (.2705″) 2.41 (.095″)  7.077(102.6) 516 .25 mm 6.35 (.250″)  2.34 (.092″)  6.937 (100.6) withcompound

[0056] The can ends may be economically made of thinner metal ifpressure retention requirements permit because these can ends have arelatively small centre panel in a stiffer annulus.

[0057]FIG. 9 shows a can 12 a, closed according to this invention,stacked upon a like can 12 b shown sectioned so that stacking of theupper can on the lower can end is achieved by a stand bead 31 a of theupper can fits inside the chuck wall 24 of the lower can end with theweight of the upper can resting on the double seam 34 of the lower canend.

[0058] The clearance between the bottom of the upper can body and lowercan end may be used to accommodate ring pull features (not shown) in thecan end or promotional matter such as an coiled straw or indicia.

[0059] Using the experimental data presented above, a computer programmewas set up to estimate the resistance to deformation available to ourcan ends when joined to containers containing pressurised beverage. Thelast two entries on the table relate to a known 206 diameter beveragecan end and an estimate of what we think the KRASKA patent teaches.TABLE 6 Check Re- Inner Outer Predicted Actual End SIZE Overall PanelChuck Wall Enforcing Wall Wall Cut Edge Thickness Bead DIA DIA WallLength RAD Height Height ø to O:D:ID d₂ d₁ Ratio Angle L r₃ h₃ h₄(*Denotes Contain d₂:d₁ mm mm D₂/D₁ B° mm mm mm mm Actual) PSI 206-20464.39 49.49 1.3010 33.07°  4.22 0.52 2.34 1.78 75.230 0.255 (2.535″)(1.9485″) (0.166″) (0.204″) (0.092″) (0.070″) (2.9618″) 206-202 64.3947.33 1.3604 42.69°  4.95 0.52 2.34 1.78 74.272 0.255 (2.535″) (1.8634″)(0.195″) (0.204″) (0.092″) (0.070″) (2.9241″) * 206-200 64.39 45.071.4287 50.053° 5.82 0.52 2.34 1.78 73.713 0.255 (2.535″) (1.7744″)(0.229″) (0.0204″) (0.092″) (0.070″) (2.9021″) 204-202 62.18 47.331.3137 29.78°  3.96 0.52 2.34 1.78 73.767 0.24 (2.448″) (1.8634″)(0.156″) (0.0204″) (0.092″) (0.070″) (2.9042″) 204-200 62.18 45.071.3796 40.786° 4.70 0.52 2.34 1.78 72.911 0.24 (2.448″) (1.7744″)(0.185″) (0.0204″) (0.092″) (0.070″) (2.8705″) 202-200 71.98 45.07 1.59730.266° 4.09 0.52 2.34 1.78 71.984 0.225 (2.834″) (1.7744″) (0.161″)(0.0204″) (0.092″) (0.070″) (2.834″) 206 std 64.69 51.92 1.2461 15.488°4.39 0.56 2.03 — 76.454 0.28 (2.547″) (2.044″) (0.173″) (0.022″)(0.080″) (3.010″)* KRASKA 64.39 — — 15°    2.54 0.81 1.65 2.29 78.0800.292 ESTIMATE (eg (0.100″) (0.032″) (0.065″) (0.090″) (3.074″)(0.0115″) 2.535″)

1. A can end comprising a peripheral cover hook, (23) a chuck wall (24)dependent from the interior of the cover hook, an outwardly concaveannular reinforcing bead (25) extending radially inwards from the chuckwall, and a central panel (26) supported by an inner portion (27) of thereinforcing bead, characterised in that, the chuck wall (24) is inclinedto an axis perpendicular to the exterior of the central panel (26) at anangle C between 30° and 60°, and the concave cross sectional radius ofthe reinforcing bead (25) is less than 0.75 mm.
 2. A can end accordingto claim 1 characterised in that the angle of the chuck wall (24) to theperpendicular axis is between 40° and 60°.
 3. A can end according toclaim 2 wherein the angle of the chuck wall (24) to the perpendicularaxis is between 40° and 45°.
 4. A can end according to any of claims 1to 3 characterised in that an outer wall of the reinforcing bead isinclined to a line perpendicular to the central panel (26) of the canend at an angle between −15° and +15° and the height h₄ of the outerwall is up to 2.5 mm.
 5. A can end according to any of claims 1 to 4characterised in that the reinforcing bead has an inner portion parallelto an outer portion joined by said concave radius.
 6. A can endaccording to any preceding claim characterised in that the ratio of thediameter of the central panel to the diameter of the peripheral curl is80% or less.
 7. A can end according to any preceding claim characterisedin that it is made of a laminate of thermoplastic polymer film and asheet aluminium alloy or tinplate or electrochrome coated steel.
 8. Acan end according to claim 7 characterised in that the laminatecomprises a polyethylene teraphthalate film on analuminium-manganese-alloy sheet less than 0.010 (0.25 mm) thick.
 9. Amethod of forming a double seam between a can body (12) and a can end(22) according to any preceding claim, said method comprising the stepsof: placing the curl (23) of the can end on a flange (11) of a can bodysupported on a base plate (4); locating a chuck (30) within the chuckwall (24) of the can end, said chuck having a frustoconical drivesurface (32) of substantially equal slope B° to that of the chuck wallof the can end and a substantially cylindrical surface portion (33)extending away from the drive surface; causing relative motion asbetween the assembly of can end and can body and a first operationseaming roll (34) to form a first operation seam, and thereafter causingrelative motion as between the first operation seam and a secondoperation roll (38) to complete a double seam, during these seamingoperations the chuck wall (24) of the can becoming bent to contact thecylindrical portion (33) of the chuck.
 10. A method according to claim 9characterised in that the substantially cylindrical surface portion (33)of the chuck is inclined at an angle between +4° and −4° to thelongitudinal axis of the chuck.